Extension ladder hook



June 8, 1954 G. R. NILSSON 2,680,555

EXTENSION LADDER uoox Filed Jan. 21, 1952 2 Sheets-Sheet 1 Ill June 8,1954 I R. NILSSON EXTENSION LADDER HOOK 2 Sheets-Sheet 2 Filed Jan. 21,1952' II I H Even/1o: Guano! 16mm, 441.5306

194 n/rs Patented June 8; 1954 UNITED STATES PATENT OFFICE 3 Claims.

The present invention relates to hooking arrangements for extensibleladders, which arrangement contains a hooking arm arranged to cooperatewith the rungs of the next lower ladder unit.

According to the present invention there is provided a hookingarrangement in which the hooking arm can be actuated upon by twosprings, one of which being arranged to hold the hooking arm in anoperative position and the other spring, the restoring spring, which ismore powerfully dimensioned than the one first mentioned, being arrangedto be stretched and slackened respectively by means of an adjustingmechanism working in dependence of the direction of movement of theladder unit carrying the hooking arrangement in relation to the nextlower ladder unit, the restoring spring being arranged in stretchedposition to. keep the hooking arm in an inoperative position.

These and other more detailed and specific objects will be disclosed inthe course of the following specification, reference being had to theaccompanying drawings, in which Fig. 1 is an elevational view of partsof two sec tions of an extension ladder showing ladder hooks of theinvention applied thereto;

Fig. 2 is a sectional view along the line 22 in Fig. 1;

Fig. 3 is a side view of the mechanism with the hooking arm in operativeposition;

Fig. 4 shows the same mechanism when the hooking arm engages a ladderrung;

Fig. 5 shows the same mechanism in still another position;

Fig. 6 is a front view of the hooking arrangement; and

Fig. '7 is a section along the line 1-! of Fig. 4.

Referring now more particularly and by reference characters to thedrawings, A and B designate generally two sections of a common extensionladder, the inner section A of which comprises stiles C and rungs D andouter section B of which comprises similar stiles E and rungs S. The twosections are held in slidable overlapping relation by conventionalguides G and are arranged to be adjusted relatively lengthwise in usualfashion to vary the overall length of the ladder. Such adjustments aremade in steps corresponding roughly to the distance between the rungs.For then securing the ladder sections in adjusted positions hookarrangements designated generally at H are employed.

The hook arrangement comprises a frame I, for instance rectangular, thepurpose of which is 2 to be fitted on the upper ladder unit. In saidframe a hooking arm 2, arranged to cooperate with the rungs S of theladder unit B, as well as a feeling arm 3 and a trigger 4 are provided.The hooking arm is pivoted on a shaft 5 at the upper end of the frameand so arranged, that it can be altogether enclosed in the frame I, i.e. assume a vertical position according to Fig. 5. The feeling arm 3 andthe trigger are freely mounted on a bolt 6 attached to one of the sidepieces of the frame I. The length of the arms 2 and 3 is adjusted insuch a way that the feeling arm and a hook I at the outer end of thehooking arm 2 can engage a ladder rung S of the ladder unit B at thesame time, as is shown in Fig. 4. The trigger t is arranged to be movedby the feeling arm 3 through the intermediation of a catch 8. When thefeeling arm is turned in a counter-clockwise direction, the catchmentioned engages an ear 9 on the trigger 6. On the side of the feelingarm 3 opposite to the catch 8 in relation to the bolt 6 the arm isprovided with a pin ll], which cooperates with the ear 9 at the angularturning of the feeling arm in a clockwise direction. In this way thetrigger can be adjusted from the position shown in Fig. 3 with the ear 9situated at the left edge of the frame I to the position shown in Fig.4, where the ear mentioned is situated at the right edge of the frame,and back again to the starting position in Fig. 3. The trigger is turnedapproximately The trigger can be actuated by two springs H and I2. Thespring II is coupled to a peg 13 on the ear 9 and at its other end to anarm l4, firmly fixed to the hooking arm 2. This spring works as arestoring spring for the restoring of the hooking arm 2 from anoperative position to an inoperative position and is more powerfullydimensioned than a spring 1'5, which works to move the arm 2 outwards tothe operative position shown in Fig. 3. The spring H5, at one of itsends, is coupled to an arm it fixed on the hooking arm 2 and at itsother end connected with a peg ll inserted in the frame I. The spring l2mentioned above is at its upper end connected with the frame and at itslower end hooked onto an ear E8 on the feeling arm 3 situated in such away that the spring [2 is working to move the feeling arm from theposition shown in Fig. 4.- downwards. In relation to the pivot bolt 6the upper end of the spring II is situated in such a way that thetrigger can be brought to pass the dead point position. The mechanism isarranged in such a way that the restoring spring H is stretched andslackened respectively by means of the trigger 4 which in its turn isdependent of the feeling arm 3 for its position. Thus, the trigger andthe feeling arm together form a setting mechanism, the functioning ofwhich is dependent upon the direction of movement of the ladder unit Ain relation to the ladder unit B.

When heightening the ladder unit A the hooking arm 2 in its operativeposition hits the rungs S with its straight outer backside and is pushedinwards into the frame I against the action of the spring when passingeach rung. In the same way, the feeling arm 3 engages the rungs with itsupper edge and is conducted downwards and inwards into the frame i byeach rung. Consequently, there is nothing to prevent the ladder unitfrom being moved upwards on the ladder unit B. Each time a rung ispassed the hooking arm 2 snaps outwards on account of the stretching ofthe spring 55, and the feeling arm 3 is restored to its outward positionby the spring 12.

When lowering the ladder unit the feeling arm 3 first engages a rung Sand is pushed upwards counter-clockwise (Fig. 4). Then the hook i slidesinto mesh with the rung, the hooking arm being pressed into a lockingengagement with same, while the feeling arm 3 being turned furthercounter-clockwise gives the trigger s such a turning angle, that the pegi3 is brought past the dead point position of the spring ii, the triggertaking the position shown in Fig. l. However, the restoring spring H isstretched with no influence on the hooking arm 2, since the position ofsame is fixed by the rung. In this manner, however, the mesh between thehooking arm and the rung is secured. If the ladder unit A is movedupwards from the position shown in Fig. 4, the hooking arm snaps inwardsinto the frame I while the feeling arm 3 is restored to its initialposition according to Fig. 3 by its spring I2. The trigger 4, however,remains in the position shown in Fig. 4 due to the engagement with astopping ledge [9 so that the hooking arm is retained in an inoperativeposition. In this condition the ladder unit can be lowered without thatthe hooking arm engages the rungs S. The feeling arm 3 is of coursemoved each time a rung passes, but this does not bring about any changein the position of the trigger, since the catch 8 just ticks over. Upona renewed upward movement of the ladder unit the upper edge of thefeeling arm 3, however, hits against the first rung S and is turnedclockwise by same (Fig. 5). In doing this the pin it on said arm engagesthe ear 9 on the trigger and turns it past the dead point position forthe spring H which spring restores the trigger to the position shown inFig. 3. The spring H is then altogether slackened, whereby the springif: can bring the hooking arm 2 to the operative position.

The mechanism described above offers the necessary safety margin fordevices of this type, since the hooking arm 2 cannot be brought toassume the inoperative position unless said arm earlier has been inengagement with a rung. Not until this has happened during which thefeeling arm has been forced upwards to the position shown in Fig. 4 isthe restoring spring ii stretched by the turning of the trigger 4 andretained in its stretched position. Thus, there is no risk that the hook7 can be brought to an inoperative position by the downwards movement ofthe ladder unit in such an in-between position of the runher, in whichthe point of the hook can be im-.

agined to accidentally catch into the side of the rung S, which issituated closest to the frame I. Should the runner accidentally startgliding from such a hooking position, the hook unfailingly catches thenext rung and goes into a normal locking engagement with same. Finallyit should be pointed out that the hook is opened up as soon as therunner is moved upwards past the first rung and remains in this openedposition so that it always retains a position of preparedness when theladder unit is again lowered.

It is apparent that the device herein described may be modified indesign and in details of construction with a view of adapting it toparticular requirements, without however departing from the spirit ofthe invention.

What I claim is:

1. An extension ladder hook mounted on a movable ladder section,comprising a hooking arm, two springs fastened to said arm, one of thesesprings being adapted to hold the hooking arm in operative position forengaging the rungs of the underlying ladder section, the other springbeing adapted to restore the hooking arm into an inoperative positionenabling the lowering of the movable ladder section, a spring actuatedfeeling arm angularly adjustable by the rungs of the underlying laddersection, a trigger adjustable by said feeling arm and connected withsaid restoring spring and arranged to stretch said spring when turned.

2. An extension ladder hook mounted on a movable ladder section,comprising a hooking arm, two springs fastened to said arm, one of thesesprings being adapted to hold the hooking arm in operative position forengaging the rungs of the underlying ladder section, the other springbeing adapted to restore the hooking arm into an inoperative positionenabling the lowering of the movable ladder section, a spring actuatedfeeling arm angularly adjustable by the rungs of the underlying laddersection, a trigger adjustable by said feeling arm and connected withsaid restoring spring and arranged to stretch said spring when turned,said feeling arm having two catch members for adjusting said trigger,one for each adjusting direction, the catch member acting during thedownwards movement of the ladder unit being arranged to turn the triggerto a position in which said member has passed a dead point position inrelation to the fastening point of the restoring spring, the other catchmember being arranged to release said trigger during the upwardsmovement of the ladder unit, said two catch members being mutually soarranged that the feeling arm, when the trigger has passed its deadpoint position, is freely adjustable by the rungs of the next lowerladder unit during the downwards movement of the upper ladder unit.

3. An extension ladder hook according to claim 2, in which the feelingarm is actuated by a spring which is arranged to hold said arm in aresting position situated in such a way in relation to the hooking armin its operative position, that, upon lowering of the ladder unit, arung of the next lower ladder unit is inserted into said hooking arm atthe same time as the feeling arm is angularly adjusted by the same rungbringing along the trigger past its dead point position.

References Cited in the file of this patent UNITED STATES PATENTS Number

